Combination of a low-pressure mercury vapour discharge lamp and a glow discharge starter

ABSTRACT

In the combination of a low-pressure mercury vapour discharge lamp with a glow discharge starter, such combination can be made to start high voltage lamps (i.e. more than 150 volts). This is effected by the use of a filler gas for the starter comprising at least 60 percent by volume of hydrogen. In a preferred embodiment, the filler gas comprises approximately 70 percent by volume of hydrogen gas and 30 percent by volume of neon, the pressure of the filler gas being approximately 20 Torr.

United States Patent 1 Netten 1 3,745,409 July 10, 1973 COMBINATION OF A LOW-PRESSURE MERCURY VAPOUR DISCHARGE LAMP AND A GLOW DISCHARGE STARTER [75] Inventor: Adriaan Netten, Emmasingel,

Eindhoven, Netherlands [73] Assignee: U.S. Philips Corporation, New York,

22 Filed: Nov. 10,1971 21 Appl.No.: 197,389

[30] Foreign Application Priority Data Nov. 21, 1970 Netherlands 7017065 [52] US. Cl 315/100, 313/151, 313/217, 313/218, 313/226, 315/290, 3l5/DlG. 5, 337/27 [51] Int. Cl. 1105b 41/08 [58] Field of Search 315/99, 100, 290, 315/D1G. 5; 313/151, 208, 217, 218, 224,

[56] References Cited UNITED STATES PATENTS 2,536,280 l/195l Hacgele 313/151 X 2,650,278 8/1953 Foulke 315/290 X 2,678,979 5/1954 Beesc 337/27 Primary Examiner-Roy Lake Assistant Examiner-Siegfried H. Grimm Att0rney-Frank R. Trifari [5 7] ABSTRACT In the combination of a low-pressure mercury vapour discharge lamp with a glow discharge starter, such combination can be made to start high voltage lamps (i.e. more than 150 volts). This is effected by the use of a filler gas for the starter comprising at least 60 percent by volume of hydrogen. in a preferred embodiment, the filler gas comprises approximately 70 percent by volume of hydrogen gas and 30 percent by volume of neon, the pressure of the tiller gas being approximately 20 Torr.

4 Claims, 2 Drawing Figures mm 1 m ADRIAANI NEHQW GENT COMBINATION OF A LOW-PRESSURE MERCURY VAPOUR DISCHARGE LAMP AND A GLOW DISCHARGE STARTER The invention relates to a combination of a lowpressure mercury vapour discharge lamp and a glow discharge starter in which the low-pressure mercury vapour discharge lamp includes two preheated electrodes and in which for the purpose of igniting said lamp one end of one preheated electrode is connected through the glow discharge starter to one end of the other preheated electrode, the ignition voltage of the glow discharge starter being larger than the operating voltage of the discharge lamp, the glow discharge starter containing a quantity of hydrogen gas.

A combination of the kind mentioned above is described, for example, in United Kingdom Patent specification 720,864.

The volume of hydrogen gas in the glow discharge starter of the known combination is not more than approximately five percent by volume of the content of the discharge space of the starter. The main gas in this know glow discharge starter is a rare gas, namely argon.

A drawback of a glow discharge starter having this known filler gas composition is that it cannot be used for the ignition and operation of a low-pressure mercury vapour discharge lamp having an operating voltage exceeding 150 Volts. These lamps, having a relatively high operating voltage, are lamps having lengths of, for example, 2.5 metres and a luminous flux of, for example, 7,000 lumens. Ignition and operation is not readily possible because for the contact distances which are commonly used in glow discharge starters the operating voltage of the last-mentioned lamps exceeds the ignition voltage of this glow discharge starter. As a result the glow discharge starter is not inoperative during normal operation of the lamp. This has the drawback of extra losses and may even give rise to a disturbed operation of the lamp when the contacts of the glow discharge starter close again and again.

A further problem which may occur in glow discharge starters is that its re-ignition voltage, immediately after opening of its contacts, may be very low so that a new glow discharge may occur in the starter which closes the contacts again and extinguishes the already ignited discharge lamp. Especially in lamps having a relatively high luminous flux this may lead to very troublesome light flashes.

It is true that it is known to ignite low-pressure mercury vapour discharge lamps provided with two preheated electrodes and having an operating voltage larger than 150 Volts with the aid of a starter which connects that end of one lamp electrode being remote from the supply mains to that end of the other electrode being remote from the supply mains. In that case, however, not a glow discharge starter but a relatively expensive electronic starter, provided with a controlled semiconductor switching element, is used. Such an arrangement is known, for example, from French Patent Specification No. 1,581,149.

An object of the present invention is to provide a simple solution for the satisfactory ignition of a lowpressure mercury vapour discharge lamp having an operating voltage of more than 150 Volts with the aid of a glow discharge starter.

According to the invention a combination of a lowpressure mercury vapour discharge lamp and a glow discharge starter in which the low-pressure mercury vapour discharge lamp includes two preheated electrodes and in which for the purpose of igniting said lamp one end of one preheated electrode is connected through the glow discharge starter to one end of the other preheated electrode, and in which the ignition voltage of the glow discharge starter is larger than the operating voltage of the discharge lamp, and in which the glow discharge starter contains a quantity of hydrogen gas, is characterized in that the operating voltage of the lamp is more than 150 Volts and that the tiller gas for the glow discharge starter consists of hydrogen gas for at least 60 percent by volume, the glow discharge starter satisfying the condition that its ignition voltage increases as the distance between its contacts decreases.

An advantage of this combination is that a lowpressure mercury vapour discharge lamp having a relatively large luminous flux can be ignited in a simple and cheap manner. The increase in the ignition voltage as the distance between the contacts of the glow discharge starter decreases furthermore has the advantage that unwanted re-ignition of the starter immediately after opening of said contacts is prevented as much as possible. The result is that flickering of the low-pressure mercury vapour discharge lamp during the starting procedure is limited.

The combination of the low-pressure mercury vapour discharge lamp and the glow discharge starter may be connected to, for example, an alternating voltage mains of 380 Volt, 50 Herz through a ballast which consists of, for example, an inductor or an inductor in series with a capacitor. However, it is alternatively possible to connect the said combination through a ballast to a mains of lower voltage. In that case the mains voltage may be converted into a higher voltage at least during the starting procedure by means of a transformer or, for example, by means of a voltage doubling circuit. This higher voltage is then applied between the lamp electrodes.

The latter case may occur, for example, when an available voltage of 220 Volt, 50 I-lerz is insufficient to ignite the lamp.

The contacts for the glow discharge starter consist of, for example, zinc or another material conducting electricity.

In a special embodiment of an arrangement according to the invention the adjacent parts of the contacts of the glow discharge starter consist of tungsten.

This special embodiment has the advantage that the glow discharge starter may have an extra high ignition voltage as a result of the large work function of tungsten.

The filler gas for the glow discharge starter may, for example, entirely consist of hydrogen gas.

In a further special embodiment of an arrangement according to the invention the filler gas for the glow discharge starter consists of hydrogen gas for approximately percent by volume and for the remainder of neon, and the pressure of the filler gas is approximately 20 Torr.

An advantage of the last-mentioned special embodiment is that the ignition voltage of the glow discharge starter at the beginning of its lifetime is slightly decreased, so that the common occurrence of ignition voltage-increasings does not lead to an extraordinarily high ignition voltage at the end of the lifetimes of the glow discharge starter. A pressure of 20 Torr then leads to an admissible contact distance. If this point of the changing the ignition voltage during the lifetime of the starter were not considered this might imply that the lamp could not be ignited after a given period because the available voltage would then be too low to operate the glow discharge starter.

The adjacent contact parts of the glow discharge starter have, for example, a shape such that they touch each other in many areas in case of the electrically closed condition of that contact.

In a further special embodiment of the arrangement the adjacent contact parts of the glow discharge starter are bar-shaped so that these parts in the electrically closed condition of the contact of the starter touch each other in the middle and together constitute a cross.

An advantage of this embodiment is that during manufacture the electrodes can be readily aligned relative to one another.

In order that the invention may be readily carried into effect, some embodiments thereof will now be described in detail by way of example with reference to the accompanying diagrammatic drawing in which:

FIG. 1 shows an arrangement according to the invention and a ballast for the stabilisation of the discharge and furthermore connecting wires for the arrangement;

FIG. 2 shows a glow discharge starter having an envelope shown in a longitudinal cross-section. This is the glow discharge starter for the arrangement of FIG. 1.

In FIG. 1 the reference numeral 1 denotes a lowpressure mercury vapour discharge lamp having an operating voltage of approximately 180 Volts. The lamp 1 is provided with preheated electrodes 2 and 3. Electrode 2 is connected through a glow discharge starter 4 to electrode 3. The combination of lamp 1 and glow discharge starter 4 is intended for connection through a stabilisation coil 5 to an alternating voltage mains of, for example, 380 Volts, 50 Herz. This voltage is then applied across terminals 6 and 7. Starter 4 is shunted by a capacitor 8 which serves for the elimination of interference in radio signals. The glow discharge starter 4 is provided with two bimetal electrodes 9 and 10 which upon heating are curved towards each other. Electrode 9 supports a tungsten bar 11 and electrode 10 supports a tungsten bar 12 (see also FIG. 2). In the electrically closed condition of the contact of the glow discharge starter 4 the bars 11 and 12 constitute a lying cross enclosing an angle of approximately 60. Bars 11 and 12 are each approximately 3 mms long and have a diameter of approximately 1 mm.

The contact distance between the bars 1 1 and 12 was approximately 0.4 mm at room temperature (C). The glow discharge starter was filled with hydrogen (70 percent by volume) and neon percent by volume). The pressure was approximately 20 Torr.

The ignition voltage of the starter (4) was larger than 240 Volts and less than 300 Volts. The glow discharge starter thus ignited readily at the mains voltage of 380 Volts.

A reduction of the contact distance (distance 1 ll, 12)

of the glow discharge starter in steps of 0.1 mm led to ignition voltage increases of approximately 10 Volts.

Due to the large (re)-ignition voltage of the glow discharge starter 4 at a short contact distance the lamp (1 5 ignited without serious flickering.

The arrangement of FIG. 1 operated as follows. After switching on the voltage source across terminals 6, 7 a current flowed through the series arrangement 6, 5, 2, 4 (8), 3 to 7. This current evolved heat in the starter 4 which heat caused the contacts 11 and 12 to be closed. The larger electric current ignited thereby in the said series arrangement caused the electrodes 2 and 3 of the lamp 1 to be heated. By cooling of the contacts of starter 4 these contacts were subsequently opened. As a result a voltage pulse across lamp 1 was produced (by the presence of the inductor 5). When the lamp 1 did not ignite thereupon, the described procedure was repeated automatically, that is to say, an arc in the glow discharge starter 4 was again produced which heated the contacts etc..

After ignition of the lamp 1 the voltage between electrodes 2, 3 decreased to the operating voltage of l80 Volts so that the glow discharge starter 4 did not operate anymore.

What is claimed is:

1. A combination of a low-pressure mercury vapour discharge lamp and a glow discharge starter, said combination comprising: a low pressure mercury vapour discharge lamp including two preheatable electrodes, one end of one preheatable electrode of said lamp being connected through a glow discharge starter to one end of the other preheatable electrode for the purpose of igniting said lamp, the ignition voltage of the glow discharge starter being larger than the operating voltage of the discharge lamp, the glow discharge starter containing a quantity of hydrogen gas, and wherein the operating voltage of the lamp is larger than 150 Volts and the tiller gas for the glow discharge starter consisting of hydrogen gas for at least 60 percent by volume, the glow discharge starter also satisfying the condition that its ignition voltage increases as the distance between its contacts decreases.

2. A combination of a low-pressure mercury vapour discharge lamp and a glow discharge starter as claimed in claim 1, wherein the adjacent parts of the contacts of the glow discharge starter consist of tungsten.

3. A combination of a low-pressure mercury vapour discharge lamp and a glow discharge starter as in claim 1, wherein the tiller gas for the glow discharge starter comprises approximately 70 percent by volume of hydrogen gas and approximately 30 percent by volume of neon, the pressure of the filler gas being approximately 20 Torr.

4. A combination of a low-pressure mercury vapour discharge lamp and a glow discharge starter as claimed in claim 1, wherein the adjacent contact parts of the glow discharge starter-are bar-shaped and that these parts touch each other in the middle, and together constitute a cross, in the electrically closed condition of the contact of the starter. 

1. A combination of a low-pressure mercury vapour discharge lamp and a glow discharge starter, said combination comprising: a low pressure mercury vapour discharge lamp including two preheatable electrodes, one end of one preheatable electrode of said lamp being connected through a glow discharge starter to one end of the other preheatable electrode for the purpose of igniting said lamp, the ignition voltage of the glow discharge starter being larger than the operating voltage of the discharge lamp, the glow discharge starter containing a quantity of hydrogen gas, and wherein the operating voltage of the lamp is larger than 150 Volts and the filler gas for the glow discharge starter consisting of hydrogen gas for at least 60 percent by volume, the glow discharge starter also satisfying the condition that its ignition voltage increases as the distance between its contacts decreases.
 2. A combination of a low-pressure mercury vapour discharge lamp and a glow discharge starter as claimed in claim 1, wherein the adjacent parts of the contacts of the glow discharge starter consist of tungsten.
 3. A combination of a low-pressure mercury vapour discharge lamp and a glow discharge starter as in claim 1, wherein the filler gas for the glow discharge starter comprises approximately 70 percent by volume of hydrogen gas and approximately 30 percent by volume of neon, the pressure of the filler gas being approximately 20 Torr.
 4. A combination of a low-pressure mercury vapour discharge lamp and a glow discharge starter as claimed in claim 1, wherein the adjacent contact parts of the glow discharge starter are bar-shaped and that these parts touch each other in the middle, and together constitute a cross, in the electrically closed condition of the contact of the starter. 